This invention relates to a method for detecting when the driver of a motor vehicle becomes inattentive. Furthermore, the invention relates to a control unit for detecting inattentiveness of the driver of a vehicle.
Japanese document JP 09 123 790 A discloses a method in which the driver's state is monitored by comparing the distribution of the steering speed and the frequency of steering movement with set reference values. The reference values are required at the start of a journey.
Japanese document JP 07 093 678 A discloses a method for detecting tiredness of the driver of a vehicle, in which method a steering inactivity phase and a subsequent steering action are detected.
Taking this prior art as a basis, the object of the invention is to make available a method and a control unit for carrying out this method which permit more reliable detection of possible inattentiveness of the driver.
This object is achieved by means of the features of the invention claimed.
In the claimed method, a steering inactivity phase and a subsequent steering action are detected. The magnitude of the implementation of the steering action is determined by evaluating the change in the steering wheel angle over time. A measure of the severity of the inattentiveness of the driver as he steers the vehicle is acquired by evaluating the result of a logic combination of the implementation of the steering inactivity phase and the implementation of the steering action.
When detecting inattentiveness of the driver, the invention advantageously differentiates between the steering inactivity phase and a more or less violent steering action which typically follows when a state of inattentiveness is present. A state of inattentiveness is therefore assumed if both the steering inactivity phase and the following steering action are detected in combination with one another. For the acquisition of the measure of the severity of the inattentiveness, the detected implementations of both the inactivity phase and of the steering action are logically combined with one another, and the result is then evaluated.
In modern vehicles, in particular motor vehicles, a sensor is usually present in any case for sensing the steering wheel angle x. For this reason, there is advantageously in principle no need for an additional sensor to implement the described method.
The assessment of the implementation of the steering inactivity phase, that is to say its duration, is advantageously acquired by evaluating the steering wheel angle and the implementation of the steering action by sensing the maximum gradient of the steering wheel angle which occurs.
The logic combination of the implementation of the steering inactivity phase with the implementation of the steering action in order to acquire a measure of the severity of the inattentiveness of the driver is carried out, for example, by means of a multi-dimensional operator. This logic combination is advantageously carried out only if both the steering inactivity phase and the anticipated subsequent steering action each occur with a predetermined minimum implementation. If the steering inactivity phase or the steering action are not implemented to a sufficiently high degree, it is assumed that the driver is not in a state of inattentiveness.
In one advantageous embodiment of the invention, the result of the logic combination, that is to say for example the result of the operator logic combination, can be mapped onto a probability value using a sigmoid function. In this way it is possible to specify the probability, between 0% and 100%, that the driver was inattentive at a specific time when he was steering the vehicle.
In order to increase the reliability of a conclusion about the attentiveness or inattentiveness of the driver of the vehicle, it is recommended not only to evaluate a result of the logic combination but instead to support this conclusion on a plurality of such logic combination results. In this context it is possible to draw a conclusion about the inattentiveness of the driver more reliably, since each result which results from a logic combination is weighted with an assigned weighting factor in order then ultimately to acquire an averaged logic combination result from the available plurality of weighted logic combination results by mathematically forming mean values. This averaged logic combination result then represents, compared to a nonaveraged logic combination result, a more reliable measure of the severity of the inattentiveness of the driver at a specific time when he is steering the vehicle.
Finally, it is advantageous if, in particular, the driver of the vehicle is informed about the detected inattentiveness in the form of a visual or acoustic warning message.
The inattentiveness of the driver advantageously is determined as a function of at least one driver-specific parameter. This driver-specific parameter is determined within a time interval Ti during the journey. It is advantageous here that the inattentiveness can also be determined during the time interval Ti during which the at least one driver-specific parameter is being determined. It is thus possible, if appropriate, also to warn the driver during the time interval Ti.
It is particularly advantageous for the at least one driver-specific parameter to be determined during a plurality of time intervals Ti. A first time interval Ti can lie, for example, at the start of the journey. It is then possible to determine the at least one driver-specific parameter during continuous subsequent time intervals Ti. This permits the driver-specific parameter to be correspondingly adjusted continuously. Likewise it is possible to determine the at least one driver-specific parameter only during specific time intervals Ti which do not follow one another.
In one advantageous embodiment of the invention, the at least one driver-specific parameter relates to a measure of the inattentiveness at which the information is output to the driver of the vehicle. As a result the so-called triggering threshold, starting from which a warning is issued to the driver, is set on a driver-specific basis and as a function of the instantaneous state of the driver.
As a result, the detection reliability of driver-specific properties is advantageously improved significantly. The adaptation is no longer restricted to the starting phase; rather, changes over relatively long distances are also taken into account. This is important in the case of inattentiveness, and in particular in the case of the detection of tiredness, since these factors are to be considered particularly critical on long journeys.
Further advantageous refinements of the method are also claimed.
The abovementioned object of the invention is also achieved by means of a control unit for carrying out the described method. The advantages of the solution correspond to the advantages mentioned above with respect to the described method.